In the process of tire production, a green tire is placed into a tire mold and subjected to heat and pressure. Typically, the tire mold is formed from two halves that fold or join together with the tire located therebetween. Steam is used to heat the mold and an internal bladder is pressurized to force the green tire firmly against the tire mold for a predetermined period of time during which the tire is cured while features are molded into the tread and possibly the sidewalls of the tire as well.
After the predetermined period of time, the tire mold is opened to remove the tire from the mold. Parts of the mold that are used to e.g., mold grooves, sipes, and other features into the tread of the tire necessarily project into the rubber materials during the curing and molding process. In order to facilitate removal of the tire from the two halves of the mold, certain parts of the mold—sometimes referred to as tread mold segments—are movable with respect to the mold halves. As such, as the tire is removed from the tire mold, the tread mold segments can move so as to be released from e.g., the tread and sidewall and out of features such as e.g., the grooves and sipes.
Two types of constructions for tire molds can be referred to as a first type and a second type based on the position of the tread mold segments relative to each other when the two halves of the tire mold are separated so as to open the tire mold. In a first type, the tread mold segments of either mold half are typically biased away from each other and towards the line of separation of the mold halves when the mold is opened and the tire is removed. When such mold is closed, the tread mold segments are forced back into contact with each other and against the biasing.
In a second type, the tread mold segments of either mold half are typically biased into contact with each other and away from the line of separation of the mold halves when the mold is open and a tire is removed. More particularly, as a cured tire is removed from the mold, the tread mold segments can move so as to release the tire. For example, the tread mold segments may be movable towards the line of separation of the mold halves and away from each other whereby the tire can be separated from the mold halves. However, once separated from the tire, the tread mold segments are biased back into a position away from the line of separation of the tire mold and into contact with each other.
For the second type, certain problems can occur during molding operations. As the tire is removed after a curing operation, the tread mold segments are biased back into contact with each other as just described. Unfortunately, as the tread mold segments return to this original position, contact between the sides of the tread mold segments can cause damage. This problem can be particularly acute in the manufacture of tires having complex features molded into the sidewalls. These features can cause the tread mold segments to “stick” as the tire is lifted out of the mold and drag one or more of the tread mold segments even further from their original position. Once released, the tread mold segments are biased back to the original position with even greater force, which can damage the tread mold segments at locations where they come into contact with each other. Such damage can scar the tread mold segments and negatively affect the appearance of the tire. This second type of tire mold is used only by way of example of one of the problems in the art. Other tire mold types can also have problems with damage between mold segments.
Accordingly, a tire mold having features for protecting the tread mold segments would be useful. More particularly, a tire mold having features for protecting the tread mold segments from damaging each other as they return into contact with each other upon removal of the tire would be beneficial.